class Nstr:
    def __init__(self,str):
        self.str=str
    def __sub__(self, other):
        new=''
        for each in self.str:
            if each !=other.str:
                new+=each
        return new


a=Nstr('I love FishC.com!iiiiiii')
b=Nstr('i')
print(a-b)